In biology, an organism is any contiguous living system (such as animal, fungus, micro-organism, or plant). In at least some form, all types of organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole.

An organism may be either unicellular (a single cell) or, as in the case of humans, comprise many trillions of cells grouped into specialized tissues and organs. The term multicellular (many cells) describes any organism made up of more than one cell.

All organisms living on Earth are divided into the eukaryotes and prokaryotes based on the presence or absence of true nuclei in their cells. The prokaryotes represent two separate domains, the Bacteria and Archaea. Eukaryotic organisms are characterized by the presence of a membrane-bound cell nucleus, and contain additional membrane-bound compartmentalization called organelles (such as mitochondria in animals and plastids in plants, both generally considered to be derived from endosymbiotic bacteria). Fungi, animals and plants are examples of kingdoms of organisms that are eukaryotes.

In 2002 Thomas Cavalier-Smith proposed a clade, Neomura, which groups together the Archaea and Eukarya. Neomura is thought to have evolved from Bacteria, more specifically from Actinobacteria.

All organisms consist of monomeric units called cells; some contain a single cell (unicellular) and others contain many units (multicellular). Multicellular organisms are able to specialize cells to perform specific functions. A group of such cells is a tissue, and in animals these occur as four basic types, namely epithelium, nervous tissue, muscle tissue, and connective tissue. Several types of tissue work together in the form of an organ to produce a particular function (such as the pumping of the blood by the heart, or as a barrier to the environment as the skin). This pattern continues to a higher level with several organs functioning as an organ system to allow for reproduction, digestion, etc. Many multicell organisms consist of several organ systems, which coordinate to allow for life.

Plant Kingdom: organisms that make their own food and do not actively move around.
Instead of Phyla, the Plant Kingdom is split into Divisions. Each Divsion group contains organisms that have things in common. Below is a list of some plant Divisions:

Magnoliophyta Division: All "flowering" plants. These plants have leaves, stems, and roots. After flowering, they form fruits with seeds. Includes most crops, trees, shrubs, grasses, garden plants, and weeds.

Fungi Kingdom: organisms that absorb food from living and non-living things.
Just like Plants, the Fungi Kingdom is split into Divisions instead of Phyla. Each Divsion group contains organisms that have things in common. Below is a list of some fungi Divisions:

Basidiomycota Division: Many different forms, most of which help decompose and break down wood, litter, and animal poop. Includes: Mushrooms, Puffballs, Rusts, and Jelly Fungus.